Fluid for fluid pressure systems



Patented Aug. 14, 1945 FLUID FOR FLUID PRESSURE SYSTEMS Charles E. Allderdice, Jr., Chicago, Ill., assignor to The Bell 00., Inc., Chicago, 111., a corporation of Illinois No Drawing. Application January 31, 1944, Serial No. 520,546

1 Claim.

My invention relates to a fluid for use'in operating and controlling fluid pressure systems in airplanes for the operation of hydraulic brakes, ailerons, tail fins, wing flaps and shock absorbers.

Among the objects of my invention is to provide fluids for fluid pressure systems having an extremely high boiling point so that systems using them may be able to operate normally in the excessive temperatures found in the Sahara desert and other hot places in the world.

In addition, my fluids also have extremely low pour points, so that systems using them may perate satisfactorily in very low temperatures.

My fluids having both extremely high boiling points and extremely low pour points, may be used in systems shifted quickly from one temperature extreme to another, without the liquids in the systems being changed. This often takes place in airplanes passing from the sub-zero temperatures of the stratosphere to the extremely hot surface temperatures of the equatorial tropics. I

In the normal operating. temperatures and in the extremely high and low temperatures found on earth, my fluids retain an operable viscosity. In extreme heat my fluids retain suflicient thickness of body to prevent their leaking past the pistons and losing hydraulic pressure. With my fluids there is no boiling at high earthly temperatures so as to cause vapor lock in the systems. Even extreme cold does not so thicken my fluids that they stop flowing Or flow too slowly to properly operate the hydraulic systems.

My fluids do not corrode any of the metal parts of a fluid pressure system, and in fact, act as a lubricant for the moving parts of the system.

My fluids have a high flash point, it being in excess of 290 F., when tested in the Cleveland open cup flash tester, and are therefore safe from combustion in ordinary handling, transit and storage throughout the highest known temperatures of the earth.

My invention also contemplates such other objects, advantages and capabilities as will later more fully appear and which are inherently possessed by m invention.

While I have disclosed herein certain preferred embodiments of my invention, yet I wish it understoodthat the same are susceptible of modiflcation and change without departing from the spirit of my invention.

The preferred form of my fluid selected to illustrate my invention consists of a solution of a mineral oil having an extremely low pour point 0! not higher than 60 F., a boiling point in excess of 500 F., a viscosity at 100 F. of between and Saybolt Universal seconds, a water white My solution has a high flash point (above 290 F.) a boiling point in excess of 500 F. and a low pour point (below 55 F.).

Referring again to my preferred solution, 1 have found that the fluid formed from the following proportions by volume is extremely eflicacious: 92% mineral oil and 8% olymerized hydrocarbon. Since my solution is made with a mineral oil which is not a fat, there is no deterioration to form fatty acids. Therefore since there is no acid, no acid neutralizeris necessary.

I may vary the proportions of my preferred fluid as follows: 98% to of mineral oil and 2% to 15% of polymerized hydrocarbon.

My solution is particularly efficacious when a used in hydraulic pressure systems in which the parts are made of synthetic rubber. In the airplanes made today synthetic rubber is specified and used.

My solution has an aniline point of at least 175 F., thus assuring a sllfilciently low aromatic hydrocarbon content so that my solution has practically no swelling action nor deteriorating effect on such synthetic rubber parts.

Having thus described my invention, I claim:

In a fluid pressure system a fluid consisting of substantially the following proportions by volume: 92% of a mineral oil having a flash point exceeding 250 F., a boiling point above 500 F., a pour point below -60 F., a viscosity at 100 F. of between 50 and 60 Saybolt Universal seconds, and an aniline point exceeding 175 F., and 8% of a polymerized hydrocarbon. said fluid so formed having a flash point exceeding 290 F. and safe from combustion in ordinary handling, transit and storage, a boiling point in excess of 500 F. to prevent vapor lock, a pour point below -55 F. to resist freezing, a viscosity at 100 F. of betweenand Saybolt Universal seconds to prevent leaking past pistons and losing hydraulic pressure and an aniline point exceeding F. to assure a sufficiently low aromatic hydrocarbon content so that the fluid practically no swelling or deteriorating effect on synthetic rubber parts.

CHARLES E. ALLLERDICE, JR. 

